﻿//-----------------------------------------------------------------------
// <copyright file="InterceptKeys.cs" company="Simnova LLC">
//     Copyright (c) Simnova LLC. All rights reserved.
// </copyright>
//-----------------------------------------------------------------------

namespace Simnova.Collaborate.WinForm
{
    using System;
    using System.Diagnostics;
    using System.Windows.Forms;
    using System.Runtime.InteropServices;

    /// <summary>
    /// Utility Class to Listen for KeyStrokes (used to listen for a key combination to display the application when minimized)
    /// </summary>
    class InterceptKeys
    {
        public KeyComboPressedHandler OnComboPressedEvent;

        private const int WH_KEYBOARD_LL = 13;
        private const int WM_KEYDOWN = 0x0100;
        private const int WM_SYSKEYDOWN = 0x0104;

        private LowLevelKeyboardProc _proc;
        private IntPtr _hookID = IntPtr.Zero;

        public delegate void KeyComboPressedHandler(); // Declare the delegate
        private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);

        public void StartWatching()
        {
            this._proc = this.HookCallback;
            this._hookID = this.SetHook(this._proc);
        }

        public void StopWatching()
        {
            UnhookWindowsHookEx(this._hookID);
        }

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool UnhookWindowsHookEx(IntPtr hhk);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr GetModuleHandle(string lpModuleName);

        private IntPtr SetHook(LowLevelKeyboardProc proc)
        {
            using (Process curProcess = Process.GetCurrentProcess())
            using (ProcessModule curModule = curProcess.MainModule)
            {
                return SetWindowsHookEx(WH_KEYBOARD_LL, proc, GetModuleHandle(curModule.ModuleName), 0);
            }
        }

        private IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
        {
            if (nCode >= 0 && (wParam == (IntPtr)WM_KEYDOWN || wParam == (IntPtr)WM_SYSKEYDOWN))
            {
                int vkCode = Marshal.ReadInt32(lParam);

                if ((Keys)vkCode == Keys.L && ((Keys)(Keys.Control | Keys.Alt) == Control.ModifierKeys))
                {
                    if (this.OnComboPressedEvent != null)
                    {
                        this.OnComboPressedEvent();
                    }
                }

               // Console.WriteLine((Keys)vkCode);
            }

            return CallNextHookEx(this._hookID, nCode, wParam, lParam);
        }   
    }
}

